How were the Ottoman and Byzantine empires similar? A. Constantinople was the capital of both empires.
B. Islam was the official religion of both empires.
C. The middle class of both empires was large and active.
D. Women were allowed to be educated in both empires.

There was never a Byzantine Empire. It was the Roman Empire all along. Byzantine is a tag invented by Hapsburg historians in the 16th century.

Ottoman Empire, Devlet-i Âlî Osmanî, or the Supreme State of the Ottomans, was a dynastic change in the Roman Empire not a traditional conquest of one people over another people. Both sides in 1453 had Greek speaking Muslims and Christians, Turkish speaking Muslims and Christians as well as Slavic speaking Muslims and Christians in their armed forces. Generals of both sides were Greek and Turkish speaking. There was a legitimate Ottoman royal fighting for Roman Empire inside the citadel. They had been friends, partners and adversaries for 382 years next to each other. Ottoman sultan spoke both Greek and Latin and he had Roman ancestors. It was much more complex than simplistic conquests.

The new dynasty kept both the Empire title as well as Roman Emperor title, Kayser-i Rûm, for its rulers. To have diplomatic contact governments had to address Ottoman ruler as Imperator Romanum or Kayser-i Rum in letters. Accordingly European Kings had to accept they are not equal to the Emperor but to his prime minister, the Grand Vazir.

Ottoman rulers also used Persian title Pad-i Shah, Turkish titles Kaghan and Hakan, Arabic titles such as Melik, Hadim-i Harameyn or Sultan. Sultan was a unisex title for all royal family members. Caliph was not used until the 19th century for panislamic moves.

Ottoman empire therefore was legally continuation of the Roman Empire in geography, capital city, people, and state traditions. Even in public laws, for which the extra-Islamic legal system of Örf, traditional law, was expanded.

Explanation:

your answer would be (b)